Genome sequences and population genomics reveal climatic adaptation and genomic divergence between two closely related sweetgum species.

Understanding the genetic basis of population divergence and adaptation is an important goal in population genetics and evolutionary biology. However, the relative roles of demographic history, gene flow, and/or selective regime in driving genomic divergence, climatic adaptation, and speciation in non-model tree species are not yet fully understood. To address this issue, we generated whole-genome resequencing data of Liquidambar formosana and L. acalycina, which are broadly sympatric but altitudinally segregated in the Tertiary relict forests of subtropical China. We integrated genomic and environmental data to investigate the demographic history, genomic divergence, and climatic adaptation of these two sister species. We inferred a scenario of allopatric species divergence during the late Miocene, followed by secondary contact during the Holocene. We identified multiple genomic islands of elevated divergence that mainly evolved through divergence hitchhiking and recombination rate variation, likely fostered by long-term refugial isolation and recent differential introgression in low-recombination genomic regions. We also found some candidate genes with divergent selection signatures potentially involved in climatic adaptation and reproductive isolation. Our results contribute to a better understanding of how late Tertiary/Quaternary climatic change influenced speciation, genomic divergence, climatic adaptation, and introgressive hybridization in East Asia's Tertiary relict flora. In addition, they should facilitate future evolutionary, conservation genomics, and molecular breeding studies in Liquidambar, a genus of important medicinal and ornamental values.

Evolution of Cherries (Prunus Subgenus Cerasus) Based on Chloroplast Genomes.

Cherries (Prunus Subgenus Cerasus) have economic value and ecological significance, yet their phylogeny, geographic origin, timing, and dispersal patterns remain challenging to understand. To fill this gap, we conducted a comprehensive analysis of the complete chloroplast genomes of 54 subg. Cerasus individuals, along with 36 additional genomes from the NCBI database, resulting in a total of 90 genomes for comparative analysis. The chloroplast genomes of subg. Cerasus exhibited varying sizes and consisted of 129 genes, including protein-coding, transfer RNA, and ribosomIal RNA genes. Genomic variation was investigated through InDels and SNPs, showcasing distribution patterns and impact levels. A comparative analysis of chloroplast genome boundaries highlighted variations in inverted repeat (IR) regions among Cerasus and other Prunus species. Phylogeny based on whole-chloroplast genome sequences supported the division of Prunus into three subgenera, I subg. Padus, II subg. Prunus and III subg. Cerasus. The subg. Cerasus was subdivided into seven lineages (IIIa to IIIg), which matched roughly to taxonomic sections. The subg. Padus first diverged 51.42 Mya, followed by the separation of subg. Cerasus from subg. Prunus 39.27 Mya. The subg. Cerasus started diversification at 15.01 Mya, coinciding with geological and climatic changes, including the uplift of the Qinghai-Tibet Plateau and global cooling. The Himalayans were the refuge of cherries, from which a few species reached Europe through westward migration and another species reached North America through northeastward migration. The mainstage of cherry evolution was on the Qing-Tibet Plateau and later East China and Japan as well. These findings strengthen our understanding of the evolution of cherry and provide valuable insights into the conservation and sustainable utilization of cherry's genetic resources.

EST-SSR marker development based on transcriptome sequencing and genetic analyses of Phoebe bournei (Lauraceae).

High-throughput sequencing of the Phoebe bournei transcriptome was performed, and novel SSR markers were identified. A total of 73,518 nonredundant unigenes were assembled and annotated by sequence similarity searching in diverse public databases. A total of 40,853 SSRs were identified from 73,518 unigenes. Twenty-three pairs of polymorphic EST-SSR markers were selected from 98 markers and used for genetic analyses in 75 individuals from three P. bournei populations. The 23 pairs of markers could detect abundant genetic information from the samples (PIC = 0.769), and cross-species amplification was successfully performed in other related species. Three populations had high level of genetic diversity (He = 0.658 in average), of which the population YS from Jiangxi province had the most abundant genetic diversity (He = 0.722). The results of genetic structure analyses showed that the population YS from Jiangxi province had obvious genetic differences from the other two populations, and the genetic information of the population SX from Fujian province was related to that of the population LC from Guangdong province and the population YS. The transcriptomic resources and EST-SSR markers are valuable tools not only for the ecological conservation of P. bournei but also for phylogenetic studies.

Genetic Analysis and Construction of a Fingerprint for Licensed Triadica sebifera Cultivars Using SSR Markers.

Triadica sebifera is an important landscaping tree species because of its colorful autumn leaves. In recent years, some cultivars have been bred and licensed, but it can be difficult to identify them from their morphological traits due to their similar phenotypes. To explore the genetic relationships and construct a fingerprint of the cultivars, the licensed T. sebifera cultivars were analyzed using SSR markers. A total of 179 alleles were identified among the 21 cultivars at 16 SSR loci, and these alleles exhibited a high level of genetic diversity (He = 0.86). The genetic variations mainly occurred among cultivars based on an analysis of molecular variance (AMOVA). According to phylogenetic analysis, principal coordinate analysis (PCoA), and Bayesian clustering analysis, the genetic relationships were independent of geographic distances, which may be mainly due to transplantations between regions. Some cultivars with different leaf colors showed obvious genetic differentiation and may be preliminary candidates for cross-breeding. Finally, the fingerprint for the licensed cultivars was constructed with two SSR markers. The results of this study can provide technical support for the application and legal protection of licensed Triadica sebifera cultivars.

Identification and Expression of the MADS-box Gene Family in Different Versions of the Ginkgo biloba Genome.

MADS-box transcription factors play important roles in many organisms. These transcription factors are involved in processes such as the formation of the flower organ structure and the seed development of plants. Ginkgo biloba has two genome versions (version 2019 and version 2021), and there is no analysis or comparison of the MADS-box gene family in these two genomes. In this study, 26 and 20 MADS-box genes were identified from the two genomes of Ginkgo, of which 12 pairs of genes reached more than 80% similarity. According to our phylogenetic analysis results, we divided these genes into type I (Mα and Mγ subfamilies) and type II (MIKC and Mδ subfamilies) members. We found that both sets of genomes lacked the Mß gene, while the MIKC gene was the most numerous. Further analysis of the gene structure showed that the MIKC genes in the two genomes had extralong introns (≥20 kb); these introns had different splicing patterns, and their expression might be more abundant. The gene expression analysis proved that GbMADS genes were expressed to varying degrees in eight Ginkgo biological tissues. Type II GbMADS genes not only were found to be related to female flower bud differentiation and development but also are important in seed development. Therefore, MADS-box genes may play important roles in the development of Ginkgo reproductive organs, which may suggest a genetic role in sexual differentiation. This study further contributes to the research on MADS-box genes and provides new insights into sex determination in Ginkgo.

Chromosome-Level Assembly of Flowering Cherry (Prunus campanulata) Provides Insight into Anthocyanin Accumulation.

The flowering cherries (genus Prunus, subgenus Cerasus) are popular ornamental trees in China, Japan, Korea, and elsewhere. Prunus campanulata Maxim. is an important species of flowering cherry native to Southern China, which is also distributed in Taiwan, the Ryukyu Islands of Japan, and Vietnam. It produces bell-shaped flowers with colors ranging from bright pink to crimson during the Chinese Spring Festival from January to March each year. We selected the P. campanulata cultivar "Lianmeiren", with only 0.54% of heterozygosity, as the focus of this study, and generated a high-quality chromosome-scale genome assembly of P. campanulata by combining Pacific Biosciences (PacBio) single-molecule sequencing, 10× Genomics sequencing, and high-throughput chromosome conformation capture (Hi-C) technology. We first assembled a 300.48 Mb genome assembly with a contig N50 length of 2.02 Mb. In total, 28,319 protein-coding genes were predicted from the genome, 95.8% of which were functionally annotated. Phylogenetic analyses indicated that P. campanulata diverged from a common ancestor of cherry approximately 15.1 million years ago. Comparative genomic analyses showed that the expanded gene families were significantly involved in ribosome biogenesis, diterpenoid biosynthesis, flavonoid biosynthesis, and circadian rhythm. Furthermore, we identified 171 MYB genes from the P. campanulata genome. Based on the RNA-seq of five organs at three flowering stages, expression analyses revealed that the majority of the MYB genes exhibited tissue-specific expression patterns, and some genes were identified as being associated with anthocyanin accumulation. This reference sequence is an important resource for further studies of floral morphology and phenology, and comparative genomics of the subgenera Cerasus and Prunus.

The complete chloroplast genome of Prunus takasagomontana, a deciduous flowering cherry native to Taiwan island.

Prunus takasagomontana Sasaki 1931 is a deciduous flowering cherry endemic to Taiwan island, China. Here, we first report the complete chloroplast genome of P. takasagomontana. The complete chloroplast genome of P. takasagomontana is 157,946 bp in length, which is comprised of a pair of inverted repeat (IR) regions of 26,437 bp, a small single-copy (SSC) region of 19,145 bp, and a large single-copy (LSC) region of 85,927 bp. A total of 129 genes are annotated, including 84 protein-coding genes, 37 tRNA genes, and eight rRNA ribosomal genes. The phylogenetic analysis showed that P. takasagomontana is sister to P. serrulata var. spontanea.

The chromosome-scale genome sequence of Triadica sebifera provides insight into fatty acids and anthocyanin biosynthesis.

The Chinese tallow tree (Triadica sebifera) can produce oil with high content of unsaturated fatty acids in seeds and shows attractive leaf color in autumn and winter. Here, the 739 Mb chromosome-scale genome sequence of the Chinese tallow tree was assembled and it reveals the Chinese tallow tree is a tetraploid. Numerous genes related to nutrition assimilation, energy utilization, biosynthesis of secondary metabolites and resistance significantly expanded or are specific to the Chinese tallow tree. These genes would enable the Chinese tallow tree to obtain high adaptability. More genes in fatty acids biosynthesis in its genome, especially for unsaturated fatty acids biosynthesis, and higher expression of these genes in seeds would be attributed to its high content of unsaturated fatty acids. Cyanidin 3-O-glucoside was identified as the major component of anthocyanin in red leaves. All structural genes in anthocyanin biosynthesis show significantly higher expression in red leaves than in green leaves. Transcription factors, seven MYB and one bHLH, were predicted to regulate these anthocyanin biosynthesis genes. Collectively, we provided insight into the polyploidization, high adaptability and biosynthesis of the high content of unsaturated fatty acids in seeds and anthocyanin in leaves for the Chinese tallow tree.

The complete chloroplast genome sequence of Styrax zhejiangensis, a species with an extremely small population.

Styrax zhejiangensis is an endemic species to China and is only distributed in Jiande, Zhejiang Province. The species is on the verge of extinction. The chloroplast genome of S. zhejiangensis was determined from Illumina pair-end sequencing data. The sequence was 157,387 bp and consisted of one large (LSC, 87,193 bp) and one small (SSC, 18,286 bp) single-copy region region, separated by a pair of inverted repeat (IR, 25,954 bp) regions. The sequence included 116 genes, including 82 protein-coding genes, 19 rRNAs and 15 tRNAs. The overall GC content was 37.0%. A maximum likelihood phylogenetic analysis showed that Styracaceae was more closely related to Symplocaceae than to Ebenaceae.

Transcriptome sequencing and SNP detection in Phoebe chekiangensis.

BACKGROUND: Phoebe chekiangensis is a rare tree species that is only distributed in south-eastern China. Although this species is famous for its excellent wood properties, it has not been extensively studied at the molecular level. RESULTS: Here, the transcriptome of P. chekiangensis was sequenced using next-generation sequencing technology, and 75,647 transcripts with 48,011 unigenes were assembled and annotated. In addition, 162,938 putative single nucleotide polymorphisms (SNPs) were predicted and 25 were further validated using the Sanger method. CONCLUSION: The currently available SNP prediction software packages showed low levels of correspondence when compared. The transcriptome and SNPs will contribute to the exploration of P. chekiangensis genetic resources and the understanding of its molecular mechanisms.

Complete chloroplast genome sequences of two endangered Phoebe (Lauraceae) species.

BACKGROUND: Phoebe (Lauraceae) comprises of evergreen trees or shrubs with approximately 100 species, distributed in tropical and subtropical Asia and Neotropical America. A total of 34 species and three varieties occur in China. Despite of economic and ecological value, only limited genomic resources are available for this genus. RESULTS: We sequenced the two complete chloroplast (cp) genomes of Phoebe chekiangensis and P. bournei using Illumina sequencing technology via a combined strategy of de novo and reference-guided assembly. We also performed comparative analyses with the cp genomes of P. sheareri and P. sheareri var. oineiensis previously reported. The chloroplast genomes of P. chekiangensis and P. bournei identically contain 112 genes consisting of 78 protein coding genes, 30 tRNA genes, and 4 rRNA genes, with the size of 152,849 and 152,853 bp, respectively. From the two chloroplast genomes, 131 SSRs were identified and 12 different SSRs located in five protein coding genes. The analysis showed the extremely conserved structure of chloroplast genomes with surprisingly little variations at the LSC/IR and SSC/IR boundaries. Moreover, the mean nucleotide diversity was found to be 0.162% for 77 regions, suggesting an extraordinarily low level of sequence divergence. Four highest divergent regions (trnH-psbA, rps14-trnT, petA-psbJ, ccsA-ndhD) with the percentage of nucleotide diversity higher than 0.50% were identified, which had potential use for species identification and phylogenetic studies. CONCLUSION: This study will facilitate our understanding of population genetics, phylogenetic relationship and plant evolution of Phoebe species.

[Clinical effect of percutaneous poking and tension band splint fixation for treatment of the calcaneal fracture].

OBJECTIVE: To observe the clinical efficacy of percutaneous poking tension band splint fixation for the treatment of calcaneal fractures. METHODS: From September 2007 to February 2009,40 patients with calcaneal fractures (42 feet) were treated by percutaneous poking reduction, including 28 feet of male and 14 feet of female, with an average age of 34.2 years ranging from 18 to 55 years. The course was from 2 hours to 7 days. All fractures were fresh and closed intra-articular calcaneal fractures. Patients were divided into two groups according to fixation methods, plaster fixation in 20 feet, tension band splint in 22 feet. Three aspects including the heel of the foot and ankle width of recovery, functional recovery, complications were compared according to the United States Orthopedic Foot and Ankle Society clinical score. RESULTS: These 40 patients were followed-up for 6 months to 2 years with an average of 9 months. The calcaneal width of the recovery, the functional recovery and force line of tension band splint group were all better than that of plaster fixation group (P < 0.05); There were no significant differences in pain between two groups (P > 0.05). Occurrence of complications in tension band splint group were lower than that of plaster fixation group (P < 0.05). CONCLUSION: Percutaneous poking tension band splint have advantage of stable calcaneal width and fewer complications on treatment of calcaneal fractures.